Beam convergence apparatus for tri-color kinescope



` s sheets-sheet 1 O. H. SCHADE l BEAM CONVERGENCE APPARATUS FOR TRI-COLOR KINESCOPE Filed April 29, 1955 Oct. 7, 1958 Oct.l7, 1958 Y o. H. SCHADE 42,855,542.

' Filed 'April 29, 1955 BEAM coNvERGENcE APPARATUS FoR TR1-COLOR KINEscoPE l :s sheets-sheet 2 ff/2 /li A v Z4/lawill* A f/ff l IN V EN TOR.

By 01mm Mmm/fr Oct. 7, 1.958 o. H. SCHADE 2,855,542 BEAM coNvERGENcE APPARATUS Foa TR1-COLOR KINEscoPE Filed April 29, 1955 s sheets-sheet s IN V EN TOR.

rra/My United States BEAM CONVERGENCE APPARATUS FOR TRI-COLOR KINESCOPE Otto H. Schade, West Caldwell, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application April 29, 1955, Serial No. 504,901

9 Claims. (Cl. 3l5-13) screen as part of a target electrode structure in which different phosphor areas produce differently colored light when excited by electron beam components impinging upon it from different angles, the angle of impingement determining the particular color of the light produced by the phosphor areas. The invention also pertains, for example, to a kinescope of the type described in an article entitled A One Gun Shadow Mask Color Kinescope7 by R. R. Law, published inthe Proceedings of the I. R. E., volume 39, No. l0, October 1951.

It is necessary for the satisfactory operation of such kinescopes to effect substantial convergence of the different electron beam components at all points of the raster scanned thereby at the target electrode. In general, this convergence may be effected by means of apparatus such as that disclosed in an article entitled, Deflection and Convergence in Color Kinescopes by A. W. Friend, published in the same issue of the Proceedings of the I. R. E. cited above. Such beam convergence apparatus includes an electron-optical system by which to control the beam convergence angles. The electron-optical system is variably energized as a function of the Vradial angle of beam deflection.

Another type of apparatus `for controlling the convergence of a plurality of electron beam components and with which the present invention is more particularly concerned comprises, in general, means for producing a plurality of electron beam components which traverse pre-deflection paths that are spaced respectively about the longitudinal axis of the tube and individual electro-magnetic means located respectively adjacent to the pre-deflection beam paths and of such character as to be energizable directly from the beam deflection circuitry in a manner to effect the desired beam convergence. In this fashion, the beam convergence angle may be varied in a manner suitable to maintain the desired beam convergence at all points in the scanned raster. It has been customary to provide, in connection with the type of apparatus alluded to, a convergence control for the several beam components in the nature of a direct current (i. e. static) convergence in order to effect proper convergence of the several beam components at the center of the screen. That is to say, in addition to the electromagnetic means described above which are provided for dynamic convergence, of the beam components, it has also been found desirable to compensate in a static fashion lfor misalignmentof the electron beam comaftflt ICC ponents which may result from manufacturing variations and the like.

As will be pointed out more fully hereinafter, the deflection of an electron beam per unit of magnetic field intensity varies inversely as a function of the potential gradient within which the beam is operating. That is to say, if the intensity of an electromagnetic deflection field is maintained constant, but the voltage of the electron beam being deflected decreases, the beam will be deflected a greater amount. It has, therefore, been found necessary to employ rather elaborate arrangements for regulating the high Voltage applied to the target or final anode of the kinescope whose beams are being converged, for otherwise misconvergence of the electron beams will result from differing deflection per unit of magnetic field intensity with differing high voltage. In the interest of efficiency, most present day television horizontal deflection circuits include means such as a power amplifier tube for driving a sawtooth current waveform through some form of transformer which couples the sawtooth energy to the raster scanning deflection coils. Through the` agency of a voltage step-up winding, the flyback pulses produced in the circuit inductances during the scanning retrace intervals are applied to a rectifier tube and filtered to afford a high unidirectional potential suitable for application to the final anode of the kinescope. Where the high voltage must thus be regulated, as through the agency of an absorption type voltage regulator which maintains a constant power load on the high voltage source, there is imposed a continuous peak power load on the deflection system which increases the power demands upon the scanning tube and the low voltage B-jsupply.

It is an object of the present invention to provide means for obviating or, at least, minimizing regulation of a high voltage power supply for a kinescope, insofar as the dependency of deflection upon high voltage provision is concerned.

Another and more specific object of the invention is the provision of novel static lbeam convergence means which, by their nature, eliminate the necessity for apparatus for regulating the high voltage supply which energizes the target electrode of a kinescope.

Stated otherwise, it is an object of the present invention to provide means for maintaining beam convergence independent of high voltage changes.

In general, the present invention, as employed in conjunction with the beam convergence apparatus of a tricolor kinescope, comprises electromagnetic windings for effecting static beam convergence and means for energizing such windings in part by rectified deflection energy and in such manner as to provide an established relation between high voltage and the static convergence field strength. As will be appreciated, the present invention permits substantial simplification of high voltage and deflection circuitry.

Additional objects Aand advantages of the present invention will become apparent to those skilled in the art from a study of the following detailed description of the accompanying drawing, in which:

Figure 1 illustrates, by way of block diagram, a color television receiver embodying the principles of the present invention;

Figure 2 is a vertical sectional view taken along line 2 2 of Figure 1;

Figure 3 is a schematic diagram of circuitry for performing certain of the functions indicated in Figure 1 in accordance with the invention;

Figures 4 and 5 illustrate schematically additional forms of the invention; and

Figures 6, 7 and 8 illustrate further forms of the nvention.

As used herein. it will be understood that the term beam components denotes either a plurality of individual electron beams emanating respectively from a plurality of electron guns or from a single electron gun provided with suitable apparatus for forming several individual beams and, in addition, those components of a single electron beam to which is imparted a spinning motion so as to trace a substantially conic locus at different positions thereof.

Reference now will be made to Figure 1 for the` general description of an illustrative color television receiver embodying an electron beam convergence system in accordance with the present invention. Composite color television signals which may, for example, be of the type set forth in the standards promulgated by the Federal Communications Commission on December 17, 1953 are intercepted by anV antennar 1,0 and applied to the input terminals of a television tuner section 12 which may be understood. as including radio frequency amplification stages, a mixer or converter, intermediate frequency amplifer stages and the second orY video detector. The deteeted composite color television signal is, in. turn, applied to a video signal processing channell 14 which performs the function of deriving therefrom video signals representative, respectively, of the component colors of an image (e. g. red, green and blue). Such color video signals are available at the leads 16, 18 and 2 0. Circuitry for performing the functions of blocks 12 and 14 may be found, for example, in the bookV entitled, Practical Color Television for the Service Industry, revised edition, April 1954, second` edition, first printing, published by the RCA Service Co., Inc., a Radio Corporation of America subsidiary.

The video signals detected within the receiver portionl 12 are or may be suitably clipped to provide horizontal and vertical synchronizing pulses for application to the sync separator circuit 22. The horizontal sync pulses then appearing at the output terminal of the sync` separator circuit are applied for synchronization of the horizontal deflection signal generator or oscillator 24, while the vertical synchronizing pulses are applied via the lead 26 to the vertical deliectionsignal generator 28. The output of the vertical deflection generator 2,8 ist conventionally connected for driving the vertical deflection output amplifier 30 which, in turn, drives a suitable sawtooth current of television field" frequency through the terminals Y--Y andthe vertical` deflection Winding forming a part of` the` conventional electromagnetic deflection yoke 32. The output sawtoothwave of television line frequency provided by the horizontal deflection generator 24 is applied via a lead 34 `to, a` horizontaldeection output and high voltagestageA indicated` by the block 36 and to be described in greater detail hereinafter. The horizontal deflection output stage applies, via the terminals X-X, sawtooth currentA wave-formsA ofy line frequency to the deflection yoke 32 and also furnishes, in a manner to be described, a high positiveoperatingvoltage which is applied via the lead 38-to the high voltage or ultor terminal 40of the kinescope 42.

The kinescope 42 maybe of the sameV general type as that disclosed in the H; B. Law paper referred=to earlier.

It will be understood, however, that,` thekinescope may` be of other types s uch as thatshowninthe, R. R. Law paper. In either case, the kinescope 42,has.a. luminescent screen 43 provided with a multiplicity of small phosphor areas arranged in groups and capable, respectively, when excited by an electron beam, f produc'zingllight` inthe different component colors in which the,Y image is-` to be` reproduced. The,lurnnescentscreenmay, as shown, be deposited directly upon therear surface of theu glass, face plate 44 of the kinescope.` In backof and spacedfrom the screen 43 is an aperturedinasking electrode 45which has an aperture for and in alignment'with each group of phosphor areas of the screen. i

In the particular tube illustrated, the kinescope also has a plurality of electron guns, equal in number to the number of' component colors in which the image is `to be reproduced. Each of these guns may 'be conventional, consisting of a cathode, a control grid electrode and a focusing electrode. Since the three guns are identical, the different parts thereof will be referred to collectively as the cathodes 46, the control grids 47 and the focusing electrodes 48. The three` electron guns produce schematically represented electron beams 49, 50 and 51 by which to energize, respectively, the blue, red and green phosphor areas of the` screen 43. When these electronbeams are properly converged at the masking electrode 45, they pass through the apertures thereof from different directions and impinge upon different phosphor areas of the various groups so as to produce blue, red and green light. It is to be noted that the size of the phosphor areas, the angles between the beams and the spacing of the mask from the screen 43 as compared with the length of` the tube are exaggerated for better illustration` of the operation of the kines'cope.

The electron-opticalapparatus of the kinescope 42 also includes a beam accelerating electrode consisting, in the present instance, of` a conductive Wall; coating 52.- formed onV the inner surface of the tubular glass neck 53 of the kinescope and extending from the region adjacent to the outer end of the focusing electrodes 48 to the conical section 54 of the tube which, in this case,` is metallic. Suitable' electrical connection (not shown) is made at the junction of the Wall coating with the, metal cone 54. The target electrode structure. including` the masking electrode 45 and the luminescent screen 43 which,rfor this purpose, may be metalized', is electrically connected tothe metal cone 54 by` suitable means` (not shown). Metallization of a luminescent screen ofthe character described' may` be etected in the manner disclosed in a paper by D. W; Epstein. and L. Pensak en-` titled, Improved Cathode Ray Tubes With Metal- Backed Luminescent Screens, published in theRCA Review, vol.` VII, March 1946.

The described electrode` structure of thekinescopemay be energized ina conventional mannerasillustrated in` which the source of energy for the cathodes, ,controlgrids and focusing electrodes is represented diagrammatically by a` battery 55 across the terminals of which there is connected a voltage divider 56. The cathodes 46are connected tof the grounded point ofA the voltageY divider and the control grids 47 are connected, to apoint=which is. somewhat negative relative to ground. Similarly, the focusing electrodes 48 are connected toapoint on, the voltage divider which may conventionally be at ahigher positive potential relative to the `grounded cathodes. The beam accelerating anode, including the` wall coating 52 andthe metal cone 54, is provided` withits highposi tive operating potential via the terminal 40 which is connected to the lead 38 from the high voltage portion of the horizontal deection output stage` 36 and which will be described more fully.

The electron beams 49, and 51 are suitably modulated in intensity under the control of the several component.color-representative video signals from the leads 16, 18 and 20. While the source of signals has been illustrated as comprising a color television receiver, it

will be understood that the video signal` source may bei a color television camera, in the event that the. kinescope 42n is employed as a monitor, for example. Also, it will be understood that the illustrated connection of the video signal source to the electron guns of the kinescope` is merely diagrammatic and thatthese connections may or may not be made directly tothe cathodes. Instead, they may be made to the grids 47 or to both the cathodes andcontrol grids.

The beam convergence system, in accordance with the' present invention, also includes a plurality of electromagnetic `eld-producing elements 4such` as :the magnets` 58 and 59mounted` around theneck 53 of the kinescope` adjacent to the pre-deflection pathsl of the electron beam components. It is to be understood that the precise location of these magnets is not necessarily indicated in the drawing. Instead, as will appear in greater detail, it is to be understood that each of these magnets is located relative to one of the electron beam components so as to iniiuence its yassociated beam component to the substantial exclusion of the others. Furhermore, it is to be understood that these magnets are of a character which, when suitably energized, produce respective fields which are transverse to the associated beam paths.

Figure 2 shows more clearly the relative positions of the convergence magnets such as 58 and 59 and, additionally, 60, relative to one another and to the electron beams with which they are respectively associated. Inasmuch as all of these magnets are substantially identical, only one of them will be described in detail.

Before describing the details of the convergence system, however, a brief description will be given of the general manner in which the apparatus functions to produce the desired result. The convergence magnets 58, 59 and 60 are energized by unidirectional energy from the static convergence energy source 61 so as to elect an initial convergence of the electron beam components substantially at the aperturedmasking electrode 45. In order to do this, the unidirectional energization of the magnets is affected in such a way that the magnets may be individually energized in different magnitudes. It is to be understood that, in effecting the initial beam convergence, the beams may be in any desired one of their different deilected positions. For example, they may be initially converged at the center of the raster to be scanned or, alternatively, they may be initially converged at one corner of the raster. The convergence magnets 58, 59 and 60 are also dynamically energized by control wave energy derived from a generator 62 so as to eiect a periodic variation of the magnitude of the transverse fields produced respectively thereby. These eld strength variations are in accordance with a predetermined function of the beam deilection. Variations in the strength of the fields produced by the convergence magnets elect corresponding variations in the paths of the electron beam components relative to the longitudinal axis Iof the tube. Hence, suitable variations are made in the convergence angles between the various beam components so as to produce the desired convergence ofthe beam components at the masking electrode 45.

The convergence magnet 58 which is associated, by way of illustration, with the blue electron beam 49 is provided with a core comprising a generally U-shaped pole piece which is so mounted as to form a continuous U-shaped magnetic path in close association with the tube neck 53. In accordance with a specific embodiment of the present invention, the convergence magnets are associated with a tri-.color kinescope having internal pole pieces. That is, and as is illustrated, a pair of radially and inwardly extending internal pole pieces is provided for each of the magnets 58, 59 and 60. The magnet 58, for example, is provided with a pair of internal pole pieces 65 and 66 associated, respectively, with the legs of the external pole piece 64. It will be understood that, by such means, the reluctance of the magnetic circuit is considerably decreased and that the ux distribution of the eld produced between the internal pole pieces 65 and 66 is considerably improved. While the present invention is illustrated herein in conjunction with a kinescope having internal pole pieces, it will be understood that its principles are also applicable to other forms of kinescopes.

The external pole piece 64 of the convergence magnet 58 is provided with electromagnetic windings 68 and `69 for dynamic energization and the static convergence field which is produced in accordance with the present invention is accomplished through the agency of the electromagnetic winding '70. Prior to describing the static convergence control of the invention, however, refer-i' ence will be made to that portion of Figure 3 of the draw'- ing which illustrates means for energizing the dynamic convergence windings of the apparatus. Since the apparatus for providing the dynamic convergence control of electron beam components does not per se constitute a part of the present invention, it will be understood that that portion of the circuitry in Figure 3 relating thereto and described herein in the interest of completeness of description is intended merely to serve as an example of suitable dynamic convergence circuitry.

In Figure 3, the energizing coils of the convergence magnets 58, 59 and 60 include the electromagnetic, dynamic convergence windings 68, 69, 72, 73 and 74, 75 connected serially in pairs and Wound about the external pole pieces of the magnets. That is to say, the windings 68 and 69 of the magnet 58 are connected in sen'es with each other and to the corresponding windings of the magnets 59 and 60. All of the dynamic windings are, moreover, connected in series with the vertical and horizontal electron beam scanning deflection circuits, substantially as indicated. As shown, the windings are coupled eectively in series with the vertical windings 76 of the deilection yoke 32 and also with the horizontal windings 77 lof the yoke. Thus, the convergence magnets may be energized dynamically as a function of both vertical and horizontal beam deection angles.

In the operation of the dynamic convergence magnet energizing portion of the apparatus of Figure 3, the vertical deilection current traversing the vertical yoke Winding 76 produces a sawtooth voltage across the resistor 78 which, as indicated, may be made variable so as to control the amplitude of the convergence control wave.

.[nductance means, such as an inductor 79 coupled to the resistor 78, has the property of performingcurrent integrating action whereby a substantially parabolic current wave at vertical deection frequency traverses the dynamic windings 68, 69, 72, 73 and 74, 75 of the con' vergence magnets 58, 59 and 60, respectively.

The resistive components of the integratinginductor 79 and another inductor 80, or horizontal frequency choke coil, in series therewith, together with the resistive com ponents of the dynamic convergence magnet windings produce a small sawtooth component in the substantially parabolic current wave traversing the circuit elements. As a result of this sawtooth component, the peaks of the parabolic wave are slightly advanced in phase or displaced slightly to the left on a time base running from left to right. The capacitor 81, connectedeiectively across the resistor 78 and the integrating inductor 79, has the eifect of producing an opposite, or retarding, phase shift by which to move the peaks of the parabolic wavev slightly to the right, relative to a time base. Accordingly, a variable resistor 82 in series with the capacitor 81 is provided so as to afford a symmetry control for the substantialy parabolic wave at vertical deection frequency in order that the convergence apparatus may be suitably operated to elfect the desired result with diierent detlection yokes.

In a somewhat similar manner, a sawtooth voltage at horizontal deflection frequency is developed across a resistor 83 which may be made variable so as to provide an amplitude control for the horizontal convergence wave. This voltage is also impressed upon the dynamic windings of the convergence magnets 58, 59 and 60 by means including a center-tapped inductor 84, at least a portion of which is connected in series with the horizontal yoke winding 77 and the resistor 83. Inductancc means, which in this case comprise the dynamic windings, function to integrate the sawtooth voltage wave to produce a substantially parabolic current wave for energization of the dynamic convergence windings of the magnets.

The deflection current in the horizontal winding 77 of the yoke 32 also produces a voltage pulse during yback or retrace intervals. This voltage pulse `is developed netic eldintensity,

' l across the. lefthandportion of theinductor 84, asrviewed';

K c K inithethawing)k and is inrjqressediuporrthe,dynamieqwindey i f i ingsofK the convergence rnagnets-.` by.y meansyincludingyar potentiometerf connected across the inductor 84. The inductance of the. zdynamicwindings causes-fr an integration i f of.. the` voltage. pulse tosform of` small;sawtooth,l current cornpome'nt.y throught thekx windings;` The.-` potentiometer i r8.4.prfovidesgaV facility for controlling thel magnitude? and f polarity ofrthe` voltage pulses impressed upon. thevcon-2 i vergencezimagnet..and/thereby functionsJ kas a symmetry:

f control for thel substantiallyparabolio; 'current`r rwave .of horizontal frequency by which thoconvergence magnets rfarefexicited., I

f Although the illustrativecircuitry."ofliigureIlfidescribediy thus fari shows .anrarrangement Ain whichV thea vertical f and;

' f 'liorizontaljconvergence waveformslflow through ,the same f windings",offthe,`electromagnets, it; shoulidgbeunderstood c l that other arrangements: in which; the` verticaljand hori lzontai rwaveforms,How through separaterwindiugs maybe satisfactorily employed; .f Additionalliy'-,`y while-f they wind.k l ings -68and 69 kareshown as. separate` coilsserially con-l f inected, it should; bey understood that a single windingk i i may be used? iniitlieiry stead; lvarious lother,v typesl and' f combinations of; windings andl separatecontrol lcircuits l yfertile dynamicconvergenceoffeach ofthe threeibeams may alsoqbesubstituted fori that shown.: -f f f f Asmentioned briefly above,y ystatic ycontrol of the elec-y f trony beam ycomponents in their pre-deflection paths is necessaryl in orderl to- 'bring'.about.properlconvergence of f thebearnsk at the centerk of the target, yfor example. lIn `the f past,l suchy static convergence control has i been dei-` pendent upon rathcr.- accurate regulation of, the high voltr age appliedfto the final.4 anode of the kinescope since, asl i 'has been pointedout, the action of `the-convergence-apparatusf whichiisin .factl a ldeflectiorzractiondependsffor its effectiveness upon the; potential of the nal anoclefofi ythe kinescope relative to the cathode thereof, -Speci-cal-- ly, the deiiectionof an relectron beam .perunitfof magy is given by the following relationship:

D la er *d1/n1., sa

where D.. is the distancewhich the beam is deected, B' is the magnetic field intensity, "1 is the axial length ofthe magnetic vdeiiecting eld, L is the distance from the;ceuter ofdeection to thefualanode or target, Ea is thepotentiahofthe final anode, e is the charge of the electron,.and,"m. is-the massof the electron; It will be seen, therefore, that :the quantity orthe magnetic deflection sensitivity varies inversely with the, square root ofthe nal anode voltage. It follows that any undesirable variation in the nal anode voltage will produce misconvergence, assuming that the magnetic field,intensity.remains-constant. In` order to prevent such-misconvergence, prior arti. ararngernents have, for example, relied upon complicated-andcostly circuitry. for regulatingl the voltage applied tothe; tinalanode of the kinescope. Moreover, such regulating circuitry undesirably` loadsttbe` deection system with-which the high voltage-producing arrangement is associated. In accordance withr the presenty invention, therefore, means are provided for` energizing` the: static convergence windings such asV 70 partially by rectified' deflection voltageand irrsuchnrianner` as toprovide` a.1/z power relation between the linalanode` voltageandthe strength of the static` convergence-afield, thereby obivating the need-for high4 voltage regulating circuits.

tn order that .the operation of the present invention i may; beirnorefafully. understood; .Figure 3 illustratesA within n the.: dotted; liner; reetangler Snar generally; conventional c c horizontal; detectionr output amplifica? circuit; including,- atypical ilybaclehigh:voltagepower; supply.k The'outputi signalof the;horizontalgdeeetion,generator 24i-s;coupled,- c c via thealeady-etr andrarcapacitorfli: to the control relectrode 9-2 of 1 therampliier; tube 94.? yA grid leakr n sistori;,connectsythepelectrode.` 92k to ground, asf; shown. i l Suitable biasngtpotential.; for@ the discharge tube ,screeny -electrode,96.`r istconventionally supplied from a;source of k l positive potentiaLindicated at terminal198; (-|-.B.) ,through n f a screendroppingresistor 100M/hieltr is,.in `turn,,b3/passed .y f y ktothe cathode 102 via aocapacitor 104. A selfebiasing.y l f f l cathode resistor lllwhosevalue isA chosen in; accordance with the. desired operating; bias` for lthe .ampliiiery tube i y :Ut is connected' in. the cathode` circnitof the; tubegantl f f isy lay-.passed by, a4 capacitor,` y 103.k `The anode 110i. ofk

- the.: amplifier. tubed isi-,connected tofaiterminal 112.505 y an-autotransformer;ltltnwhichgincludesan auxiliaryistepfy f f f up ;winding. 1116` connected .t toA fthexanode. 118 of. the, high t f voltage` .reci-tifying; diode; l120.y The. cathode 122 yof thek rectifier.: diodeeisr connected to ground through. a litter*l f f capacitor 124, gsofthat high. voltage for kthe kfinal; .anode f r ofathekinescopejlz.maybe,appliedtothehigh voltage y ermin'al 40; f yThe lower. terminus' 12d of the' autotransl f l f l f i former is ,connected through. affB-boost capacitor. 128 f Asathuszfargdescribed, kthe apparatus of the drawing isiL willffurtherrbeseen thatlthehorizontal `deflectionfiwiriding f i f f f 77 of; theraster scanning4 deflectionyoke is connected f c inshunt. withgthat-portion ofy the autotransformerr vbe-` n l n c tween theterminals 12.6;and 132.'. Alconventionaldamp; f i

ing devicecomprisingby way ,of illustration, `thediode f c f 134 liseormected inl dampingprelation rwiththe .yokewind c ing 77 throughjthe` B-boost capaictor `1123.` f .Specicallyi l the anode` 136 of the. damper.-diode134 isk connected f to the .+131 terminal :130, whilerthe ,cathode 138 ofi the i i damper tube is connected toa point 140 ionlthe autotrans-y f f f former.

in; accordance rwith* conventional practice: and, since; f f f f theoperation of`sucl1 scanning apparatus is well-known, it need not be describedin detail here. A full analysis of such` operation is given, for` example, in an article by the present applicant entitled,"Magnetic Deflection Circuits,`which appeared in the September, 1947,' issue of RCA Review. Briefly,however, it is to be noted that the bias on th'e horizontal output tube 94 isso adjusted that, during` operation, the driving saw-tooth waveform which is provided by the horizontal deflec tion generator will produce anode-cathode conduction only during aperiodcorresponding to a little more than half"the deflection cycle. Accordingly, it may be assumed that the horizontal output tube 94 is rendered conductive by the'sawtooth waveform on its control electrode during` only the second half' ofthe linescanning interval; during which interval anode-cathode current will pass from the positive power'supply terminal 130 through the diode 134, theA transformer 114 and the tube 94.` Such currentflowinducessome deflection voltage and current in the transformer whichA causes a substantially linear` rise in-detlection current through the yokewinding 77;r AtaA time'corresponding to-the commencement of the retracel orf fiyba'ck interval of* the deiiection cycle, the discharge-tube94=becornes non-conductive and the magnetic iield'iny theautotransformer and yoke will then collapse, causing oscillation of "the primary resonant circuit`f(i. e., yokegandits distributedcapacitance) at its self-resonantfrequency which is normally at leastfour or tive times that of the deflection frequency.

After one-half cycle` of free oscillation, the voltage appearing across the horizontal winding '77 will be of such polarity as to-cause the diode 134 to conduct, thereby dampingthe oscillations and aperiodically discharging the. energymagnetically stored in th'e yoke. Tliedirection of the dampingcurrentthrough the diode 134 `will be in such direction as to charge the capacitor 128v such that its terminal adjacent to the point 126 is positive with respect to the terminal 130. This current through the diode 134, in laccordance with well-known reaction scanning principles, provides the first portion of the current sawtooth through the winding 77, which portion corresponds to the first portion of' the trace interval. At the end of such interval, the horizontal discharge tube 94 will have been rendered cond-uctive and, this time, by reason of the bias across the capacitor 128, the diode will not immediately conduct, which will therefore cause most of the horizontal output tube anode current to flow through the autotransformer section between the terminals 126 and 140. It will be recognized from the foregoing that the value of the high voltage'produced at the lead 38 by the rectifier tube 120 will depend upon the amplitude of the iiyback pulses produced in the autotransformer 114 during the retrace intervals of the deliection scanning cycle. Since, from the standpoint of static convergence, it is undesirable for such high voltage to vary or uctuate, prior art arrangements have employed voltage regulating arrangements at the lead 38, for example, to maintain a substantially constant load on the rectifier 120. lt will also 'be recognized, however, that the amplitude of the flyback pulses rectified to produce the nal anode voltage is proportional to the deflection current through` the vtransformer 114, and, therefore, proportional to the amount of energy stored in the B-boost capacitor 128 yby the damper diode 134 which serves, as will be understood, as a rectifier. The present invention exploits this proportionality in controlling the static convergence energy applied to the static convergence windings 70, 70a and 70b and in a manner which will now be described.

Each of the static convergence windings 70, 70a and 70b has in series with itself one of the variable resistors 146, 146a and 146b and the several windings are connected in parallel, as shown in Figure 3. The junction of- `the variable resistors 146, 146o and 146b is c'onnected via a lead 148 to the terminal 126 which is, as shown in the drawing, connected to the positive terminal of the B-boost capacitor 128. The junction of the windingsl 70, 70a and 70b is, on the other hand, connected via a lead 150 to the adjustable slider .tap 152 of apotentiometer 154 which is connected from the B+ terminal 130 to ground, as shown. The B+ terminal 130 and the slider tap 152 are, respectively, .by-passed to ground by capacitors 155 and 156.

.l In the interest of simplicity, it may be assumed initially in .the following explanation of the operation of the circuit of Figure 3 that the voltage at the +B terminal 130 is equal to that developed across the B-boost capacitor 128-and that the slider tap 152 is at the lowermost end of the potentiometer 154 (i. e., at gro-und). It will, therefore, be appreciated that the voltage impressed across the leads 148 and 150 will 'be equal to the sum of the +B voltage and that across the B-boost capacitor and, since it has been assumed that such voltages are equal, the voltage impressed across the leads 148 and 150 will be equal to twice the B-boost voltage. Assuming now, by way of example, that the high voltage developed at the lead 138 decreases l0 percent, as by reason of an increased Ibeam current load in the kinescope 42, the boost voltage component will similarly decrease by substantially percent. The total voltage across the leads 148 and 150 (and, therefore, across the parallel-connected static convergence windings) will, however, decrease only 5 percent, since the +B voltage at the terminal 130 remains constant. That is to say, it may be assumed that a battery of the voltage required for the +B terminal is connected between the terminal 130 and ground.

It will further be seen from the foregoing example, that, while ythe high voltageat the lead 38 has decreased from 100 percent of its normal value to 90 percent (0.90), the yoltage applied across the leads 148 and 150 to the connormal value to 95 percent (i. e., 0.95) lwhich is substantially the square root of 0.90. Itwill thus be understood that a l0 percent decrease in the high voltage at the lead 38 for application to the kinescope final anode is accompanied by Ia 5 percent decrease in the voltage impressed across the electromagnetic static convergence windings, or, in other Words, the static convergence field components will vary as the square root of the high voltage, thereby satisfying the above equation which defines magnetic deflection sensitivity in terms of final anode voltage.

Throughout the foregoing description of the operation of the static convergence arrangement of Figure 3, it has been assumed that the +B voltage at the terminal 130 is equal to the B-boost voltage across the capacitor 128. Assuming, however, that the +B voltage is greater than thenormal B-boost voltage across the capacitor, the slider tap 152 may -be moved upwardly along the potentiometer 154 to provide an initial setting according to which the voltage impressed across the leads 148 and 150 is made up equally of B-boost and B+ voltages.

Where, on the other hand, the fixed B+ voltage is less than the B-boost voltage normally developed across the capacitor 128, an arrangement such as that shown in Figure 4 may be employed for providing the initial halfpower relationship between the high voltage and the convergence winding energization. In Figure 4', reference numerals identical to those employed in Figure 3 are used to identify corresponding elements. In the arrangement of Figure 4, the association of the +B terminal 130, the B-boost capacitor 128 and the damper diode 134 is the same as that set forth in connection with Figure 3. Since it is assumed that the voltage developed across the B- boost capacitor 128 in Figure 4 is .normally greater than the voltage at the B+ terminal 130, a potentiometer 160 is connected in parallel with the capacitor 128 and is provided with an adjustable slider tap 162 connected to the lead 148. Again, as in the case of Figure 3, the individual static beam convergence windings 70, a and 70b are connected, respectively, in series with the variable resistors 146, 146a and 146b which, as will be understood, serve the purpose of adjusting the individual field strengths of the several Ibeam convergence windings by varying the currents therethrough. When the slider tap 162 is at the extreme left end of the potentiometer 160 as viewed in the drawing (i. e., electrically connected to the terminall 126) the full B-boost voltage plus the B+ voltage will appear across the beam convergence windings. :By moving the slider tap 162 to the right, the amount of B-boost voltage actually 4applied across the windings may be made equal to the B+ voltage, in order that the half-power relation between the high voltage and the beam convergence winding energy may be obtained.

Once the initial setting of the slider tap 162 on the potentiometer 160 has been made so that B-boost and B+ voltages actually applied to the convergence windings are equal, the operation of the circuitry of Figure 4 is substantially identical to that described in connection with Figure 3. While its operation should, therefore, be apparent, an

example will be given in the interest of insuring such understanding. Assuming, by way of` illustration, that the high voltage developed by the rectifier tube 120 should decrease by 2O percent, the B-boost voltage developed across the capacitor 12,8 through the rectifying action of the tube 134 will also decrease by 20 percent. The total voltage (i. e., B+ plus B-boost) applied across the convergence windings will, however, be decreased by only half that amount, or l0 percent. Analyzing these gures, it may be stated that, while the high voltage developed by the rectifier has decreased from 100 percent of its normal value to percent thereof (i. e., 0.80), the beam convergence energy has decreased from 100 percent (i. e., B- boost plus B+) to percent (i. e., B+ plus 0.80 B- boost). Since 90 percent (0.90) is approximately equal tothesquare root of 80 percent (0.80)y it will be seen that the desired `square root `relationship between :the highlvolt-y age` and the convergence winding'zenergyris maintained; It: should also be'apparentffrom tlietfregoingrthat;while the` two examples givenehavefassumed'a decrease in therhigh voltage appliedzto,thetiinalranodeeo thefkinescope, corre-v sponding .resultsnare` obtained incaseof'an increased `high voltage.` That is to^say, if the highivoltage.Y should' in:- crease, theamount'of' energy provided;forfimprcssion across thezbeam'convergence windings would also increase and in such manner as :,toretain'theh'ah` power relation# ship.

While; the arrangements of Figures 3 and 4,illustrate forms of thepresent inventiontin accordance with which' the requisite; square root' relationship i betweenft th'e` 1 static beam convergence energy` andthefhiglrvolt'ageris afforded through thefuse ofgmeans forfenergizing theconvergence windings partiallyfromthe `Beboost energy usually` present in.. combined deilectiorr and` high voltage' arrangements, thereis illustratcdinrEigure: 5 another form'of the invention, namely, one in Aaccordance.` with t which :energization of the static convergence Windingszisprovidedv by auxiliary rectili'errneans.` Thoseelements oll Figure 5 corresponding to portions of Eigures 3 andu'4are identiiied byl the `sameireferencernumerals. In the arrangementoiFigure 5, the defiectionrandhigh1 voltage circuitry is the same` as inthe precedingsiigures, includingthehorizontalfoutput` tube 94g outputtransformerlli, highvoltage `rectiiier 128, damper tube V13,4, B -b'oost capacitor'128 and J-i-B terminal 130. Associated with the transformer 11.4,' however; isan auxiliary transformer'winding168 which is` so related to the transformerzthat voltage is induced therein by detlec tion-energy in` thetransformer 114. The winding 168 is serially connected, as shown, with a rectifier diode i7@` having an anode 172 and a cathode 174 and a storage capacitor 176. Thejunction of the rectifier.` cathode 174 `and the `storage capacitor 176 is connected to a lead 148 correspondingzto the lead bearing the same reference numeralin Figures 3` and 4. The junction of the transformer winding 168 and the capacitor 176, on the other hand, is connected to a slider tap 178 which is adjustably positioned on a potentiometer 180 connectedacross a source of positive potential illustrated asa battery B, A lead 150 corresponding to the lead bearing the same reference numeral in Figures 3 and 4, is connected to th'e lower terminus of the potentiometer 180l(i. el, ground)` andis designated for, connection, together-with theleadi 148, to the static convergence windingsof the electromagnets 70, 70a andf70bxin ,the manner explained in connecf' tion `with the preceding figures.

Inmthe `operation of `the apparatus of Figure 5, it will bepunderstood that the voltage inducediin the auxiliary Winding 168 bythe deflection energyof the transformer 114 will be proportional to the amount ofienergy rectified by the diode 120 to provide the nal anode voltage for'th'e kinescope. Such Voltage induced in the winding 168 has the` same polarity with respect to `diode 170` as the voltage on the maintransformerwinding hasfto diode 134. The energy from winding` 168.l will be: rectified by the1 diode-170 ,to -provide a. charge across the capacitor 176,- as shown. Assumingthatthe.` voltageof' the0 batteryB? is somewhat greater than the chargeA normally produced across, the cap,acitor:176 by rectification ofthe deflection energy, the slider tap 178 may be moved downwardly from the upper terminus of a potentiometer 180` untilithe battery-voltageabetween;the tap 178 and ground is,equal to the-,charge across thecapacitor. With thisl initial setting accomplished, the square root relationship between .the static convergence energyapplied across the leads148 and\150and thehighvoltage developed by the.recti1ier:120.will be secured. The specic'zfractional portion `of the deilection energy which is induced; in the windingu168is -not material, except insofarlas it is.neces sary to provide, sutcientvoltage-` across the leadsr148 and 150- to energize the :convergence -windings properly.

Assuming that, forsomereason, thel high voltagerpr Cit of` its normal value, or approximately the square root' In the arrangementof of the high voltage percentage. Figure 5 employing a separate winding andl rectifier for the derivation of energy for the convergence windings;

it has been assumed that the voltage ofthe battery B 1s greater than that normally developed across the capacitor 176. Where, on the other hand, the reverse situation is the case, the potentiometer may be connected across' the capacitor in the manner illustrated in Figure 4.

In each of the foregoing described forms of the invention, means have been provided in the form of variable series resistors for affording individual adjustment of the strength of the respective fields produced by the static convergence windings. Figures 6, 7 and 8, on the other hand, illustrate what may be termed mechanical (as opposed to electrical) arrangements for affording adjustability of the strength of the static beam convergence fields. InA each of Figures 6, 7 and 8, the U-shaped magnetic` external pole pieceisindicated by the reference numeral 645- and the dynamic convergence windings are shown` at 68and 69, While the static convergence winding-is'indicated'by the `numeral 70. In Figure 6, the U`- shapedexternal'poley piece 64 is provided with an adjustable shunt 184 which may, for example, be formed of` any suitable magnetic material of low reluctance. Theshunt 184is connected'at one end to the pole piece 64, as by a suitable fastening element 185. The other end of the shunt 184may be adjustably spaced from the U-shaped pole piece 64 in the region ofthe static winding 70, as through the agency of a bolt 186 threadedV throughianf aperture inthe shunt piece. Thatis to say, the shunt piece 184 Ais capable, when the bolt 186 is `fully retracted so-that the shuntlrestsat both ends on the bight ofthe U-shapedmember 64, of eectively shortcircuiting flux produced by thestatic convergence winding'70; As the bolt'186'iis threaded within the shunt' netic lield'produced within the tube between the internal pole pieces 65 and 66 is gradually increased.

Figure 7 illustrates another form of mechanicalV ad-` justment arrangement employing a magnetic shunt piece 187 which may be a rod or bar of soft iron or other magnetic material slidably received within a bore 188 in one of the legs of the U-shaped external pole piece 64. A threadedbolt 189 connected to the end of the shunt piece 187 is `threadedly received by an arm 190 offset laterally from the U-shaped member 64, so that threading of the bolt189 in one direction will cause the shunt piece 187 to move to the right as viewed in the drawing until it reaches the right hand leg ofthe U-shaped pole piece, thereby substantially short-circuiting the ilux produced by the static convergence winding 70, to decrease the strength of the static convergence ieldbetween the internalpole pieces 65 and 66 to-a minimum value. As the bolt 189 is threaded in the other direction, thereby moving the shunt piece 187 to the left as shown in the drawing, the air gap between the member-187 and the right hand leg of the U-shaped pole piece `64 will be in; creased, thereby `to increase the `strength of the effective static convergence field within thetube.

The U.,,shapedexternal pole piece 64 shown in Fig ure;8, and `havingrwound thereon the static convergence winding` 70 and the dynamic convergence windings, is

192. Each of the legs 191and 192 is provided with an arcuate recess in its surface facing the other of the legs, which recesses slidably receive therebetween a shunt piece in the form of a rod 193 of iron or other low reluctance magnetic material. When the rod 193 is fully inserted between the legs 191 and 192, an effective short circuit is provided for the flux from the winding 70 through the legs 191 and 192 and the shunt piece 190. In this event, the static convergence field produced Within the tube is of a minimum value. When, on the other hand, the shunt piece 193 is retracted, as shown, the amount of the shunting is decreased, thereby increasing the strength of the static convergence field within the tube.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

l. In combination with a cathode ray tube having a target electrode and electron gun, means for directing an electron beam toward said electrode, power supply means for applying to said target electrode a unidirectional operating voltage subject to variation; beam position controlling means comprising an electromagnetic deflection Winding associated with said tube for producing a magnetic field transversely of at least a portion of such tube to control the position of such electron beam; means for supplying said winding with energy; and means coupled to said power supply means and to said last-named means for causing such energy to Vary in percentage as a certain fractional function of the percentage of such unidirectional voltage applied to said target electrode, such that a change in such operating voltage is attended by a smaller change, percentagewise, in such energy.

2. In combination with a cathode ray tube having a target electrode and electron gun means for directing an electron beam toward said electrode, power supply means for applying to said target electrode a unidirectional operating voltage subject to variation; beam position controlling means comprising an electromagnetic deection winding associated with said tube for producing a magnetic eld transversely of at least a portion of such tubes to control the position of such electron beam; means for supplying said dellection winding with energy; and means coupled to said power supply means and to said last named means for causing such energy to vary in percentage as a square root function of the percentage of such unidirectional operating voltage applied to said target electrode, such that a change in such operating voltage is attended by a smaller change, percentagewise, in such energy.

3. In combination with a cathode ray tube having a target electrode and electron gun means for directing an electron beam toward said electrode, power supply means for applying to said target electrode a unidirectional operating voltage subject to variation; beam position controlling means comprising an electromagnetic deection winding associated with said tube for producing a magnetic eld transversely of at least a portion of said tube to control the position of such electron beam; means for supplying said deflection winding with energy; and rectier means operatively coupled to said power supply means for rectifying a portion of the energy therein and coupled to said last named means for causing the energy supplied to said deflection winding to vary in percentage as a certain fractional function of the percentage of such unidirectional operating voltage which is applied to said target electrode, such that a change in such operating voltage is attended by a smaller change, percentagewise, in such energy.

4. In combination with a cathode ray tube having a target electrode and electron gun means for directing an electron beam toward said electrode, electromagnetic deflection apparatus associated with said tube for causing such electron beam to scan across said target electrode; flyback power supply means associated with said deflection apparatus Afor deriving energy therefrom and for applying to said target electrode a unidirectional operating voltage subject to variatio-n; beam position controlling means comprising an electromagnetic deflection winding associated with said tube for producing a magnetic eld transversely of at least a portion of such tube to control the position of such electron beam in addition to the control afforded by said electromagnetic deflection apparatus; means for supplying said dellection winding with energy; and means operatively coupled to said power supply means and to said last-named means for causing the energy supplied to said winding to vary in percentage as a certain'fractional function of the percentage of such unidirectional operating voltage applied to said target electrode by said Apower supply means, such that a change in such operating voltage is attended by a smaller change, percentagewise, in such energy.

5. In combination with a cathode ray tube having a target electrode and electron gun means for directing an electron beam toward said electrode, electromagnetic beam deflection apparatus of the type having a deection winding, means operatively coupled to said winding for developing a high, unidirectional voltage from a portion of the energy in said winding and an energy storage device for receiving and storing electrical energy from said winding such that the amount of such stored energy varies as a function of the level of energy in said winding and said voltage developing means, said unidirectional Voltage being subject to variation; beam position controlling means comprising an electromagnetic deflection winding associated with said tube for producing a magnetic eld transversely of at least a portion of such tube to control the position of such electron beam in addition to the control afforded by said electromagnetic deflection apparatus; and means operatively coupling said energy storage 'device to said beam position controlling winding for energizing said winding in such manner that the energy therein varies in percentage as a certain function of the percentage variation of such unidirectional voltage applied to said target electrode so that a change in such unidirectional voltage is attended by a smaller change, percentagewise, in the energy applied to said beam position controlling winding.

6. The invention as defined by claim 5 including a source of relatively fixed voltage of value substantially equal to the nominal value of the energy stored in said storage device; means connecting said voltage source in series-aiding relationship with said energy storage device, said means operatively coupled to said beam position controlling winding being so connected to said voltage source that the energy applied to said winding comprises the sum of the voltage of said source and the energy stored in -said storage device, whereby said certain function is a fractional power.

7. In a` cathode ray tube image reproducing system wherein a plurality of electron beam components which traverse spaced pre-deilection paths which bear a predetermined relation to the longitudinal axis of such tube are angularly deflected both horizontally and vertically by electromagnetic beam deection apparatus to scan a raster on a target electrode, power supply means for applying to said target electrode a unidirectional operating voltage subject to Variation; and electron beam convergence apparatus comprising: electromagnetic means mounted adjacent to said predeilection beam paths and energizable dynamically to produce respective fields transversely of said beam paths; means coupled to said raster-scanning beam dellection apparatus in energy receiving relation thereto and to said electromagnetic beam convergence means for energizing said electromagnetic beam convergence means in such manner as to direct said beam components relative to one another and to said longitudinal tube axis so as to effect substantial convergence of said beam components at all points of such raster; and means operatively coupled to said power supply means and to said electromagnetic beam convergence means for energizing said beam convergence means with.

2f, s es; 514e@ 15 static energy variable percentage-wise as a certain-fractional function of the percentage of`- such unidirectionalvoltage applied to said target electrode, suchl that a change in such unidirectional voltage is attended by a smaller change, percentagewise', in such static energy;

8. In a` cathode ray tube image reproducing system wherein a plurality of electronbeam components which traverse spaced pre-deflection paths which bear apredetermined relationto the longitudinal axis of such tube are angularly deected both horizontally andl vertically by electromagnetic beam deflection apparatus to scan a raster on. a target: electrode; power supply means for applying to said targetelectrod'e a unidirectional operating voltage subject to variation; and electronbeam convergence apparatus comprising: electromagnetic means mounted adjacent to said predeection beamV paths and energizable' dynamically to produce respectiveelds transversely of said beam pathsymeansfcoupled to saidrasterscanning beam deflection apparatus in'` energy receiving relation theretofand to` saidielectromagnetie beam convergence means fory energizing.said electromagnetic bearnl convergence mean in suehvmanner'asl to direct saidbeam components relative to` one another and tol said longi tudinal tube axis soas` to` effect substantialconvergence of said beam components; atV all points-off such raster; and means operatively coupled to saidl power supply means and to` said electromagnetic beam` convergence means for energizing said beam-convergence meansv with static energy variable'percentageawise'as atsquarerootl function of the percentage of such unidirectional'voltagel `1&5 relationyto;` the longitudinali axisi of such .tube` are angularlyrA deected" bothi horizontally andy vertically by electrornagnetic;v beam deileetion apparatusatoll scan a raster on a: targatielectrode;.ybacle power supply means associated Witlnsaid beamtdeflection apparatus and coupled tolsaid targetelectrodeswfor applyingto saidelectrodesa unidirectional foperating voltage subjectto variation; electrornagneticJ meanst` mounted adjacent to said predeflectionz beamlpaths;` and energizable to produce respective elds transversely; of t said beam path; means coupled tosaid rasterfscanningf beam deflection apparatus in energy` receivingrelationi therewith and to said` electromagneticy beam` convergence meansl for energizing said convergence means t inlfsuch nnanner` as to directlsaid'bearn Il components relative to one another and to said longi-` appliedto said target electrode; such thatia given change' i in the magnitude of suchA unidirectional voltage is' atL tended by a smaller percentage change in' the magnitude of such static energy.

9. In a cathode ray tube imageV reproducing systemi wherein a plurality of electron beam componentswhch traverse pre-deflection paths whicltlbear afpredetermined" applied to said target-` electrode sothat a change insuch` unidirectionalL voltage is. attended by a smaller' change, percentagewise, in such` static energization.

References Cited in the file of this patent UNITED STATES PATENTS Schwarz Junef28', 1955 Parker July-19, 1955 

